Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$164.94	12.489%	$185.5394	$185.54	$185.55	$185.50
Purchase #2	$167.39	12.640%	$188.5481	$188.55	$188.55	$188.50
Purchase #3	$74.57	12.408%	$83.8226	$83.82	$83.80	$83.80
Purchase #4	$152.96	13.720%	$173.9461	$173.95	$173.95	$173.90
Purchase #5	$16.92	6.497%	$18.0193	$18.02	$18.00	$18.00
Purchase #6	$197.65	9.140%	$215.7152	$215.72	$215.70	$215.70
Purchase #7	$89.64	9.239%	$97.9218	$97.92	$97.90	$97.90
7 purchase totals =	$864.07		$963.5125	$963.52	$963.45	$963.30